Hepatitis C virus (HCV) is the most common blood-borne infection in the United States, with an overall prevalence of ~2%, and an estimated 200 million chronically infected people worldwide. A substantial body of evidence, including work from our laboratory, supports the concept that early events in the coordination and nature of multi-cellular immune responses are critical in determining whether the virus is cleared or whether persistence is established. However, very little is known about the role of non-parenchymal liver cells (NPCs) in mediating anti-HCV responses. We propose to study how plasmacytoid dendritic cells, Kupffer cells and liver sinusoidal endothelial cells sense HCV infection. We present evidence that NPCs can respond to a viral product of hepatitis C (known as a pathogen-associated molecular pattern or PAMP) by producing high levels of Type III IFNs (interferon lambda 3). These intriguing results corroborate the recent studies demonstrating genetic associations with single nucleotide polymorphisms that encode interferon lambda 3 and spontaneous recovery from HCV. Moreover, we have demonstrated that NPCs express HCV core after inoculation with virus or co-culture with infected hepatocytes. We will determine how NPC-derived proteins can inhibit viral replication. Furthermore, we will explore the specific mechanisms by which HCV core protein induces regulatory CD4+ T cells, thus linking innate and adaptive immune responses. The personnel involved in this application include graduate student, post-doctoral fellow and faculty.